lidar project - amherstgis.amherstma.gov/data/springnearc2011/d_session3/... · lidar project...
TRANSCRIPT
LiDAR ProjectMassachusetts Military Reservation
Kevin BartschCivil Engineering, Otis Air National Guard Base
Northeast Arc Users Group Spring 2011
Main Points of this Discussion
Establish some basic information about LiDARIllustrate some by-products from LiDAR dataIntroduce examples of the MMR LiDAR data
Extent of MMR LiDAR Data
102nd Intelligence WingUS Coast Guard6th Space Warning SquadronArmy National GuardMany Others
Occupants at the MMR
LiDAR Basics
Light Detection And RangingAirborne on plane or helicopterUses pulses of laser lightGPS & return time of the pulsePulse Beam is about 18”Multiple returns are collectedCreates elevation dataData is in form of X-Y-Z (UTM meters)
Possible Products from LiDAR
Triangulated Irregular Networks (TIN)Digital Elevation Models (DEM)HydrologyContoursLine-of-Site Analysis3-D RenderingsCanopy ProfilesCartographic EnhancementFeature Extraction - Buildings
Overview of Sample Area
Raw LiDAR Points (37m records)
Processed Points (Bare Earth)
Detail Area
Triangulated Irregular Networks
Digital Elevation Model
Raster Based Elevation X-Y-Z data is Interpolated into cell based dataEach cell has an elevation valueDEMs are continuousFirst step to other products
DEM (1 meter cell size)
DEM (5 meter cell size)
1 meter cell size
5 meter cell size
InterpolationNatural NeighborSplineKriging
Cell size, smoothing, neighboring cells, break lines …
Smallest Cell Size with Minimum Artifacts
1. Determine transect or posting distance (t)2. Determine test size (x) by dividing by 8 (t/8=x)3. Create test grids with cell sizes of 2x, x, x/2, x/44. Check for artifacts5. Determine scale ratio (sr) for each test grid
sr= distance of raw point to artifact/test grid cell size6. Choose smallest cell size where sr<4from: Larry Ellis et al., University of Florida, 2005 SSSA Presentation
Digital Elevation Model
Some of the neat things you can do with a DEMHillshades
SlopeAspect
HydrologyLine-of-site
Overview of Sample Area
Slope
Aspect
Detail Area for Channels
Flow Accumulation
Hillshade
Shadows that the surface would have in bright sunlightEnhances features for visual analysisMay also imply features that are not there
Hillshade
Artifacts
Hillshade Detail
Hillshade for Feature Detection
Hillshade for Feature Detection
Line of Site Analysis
DOQ draped on DEM
DOQ draped on DEM
Contours
From X-Y-Z, DEM, or TINMany algorithms – complex technologyIncorporate break lines, ponds, anthropologic features…Depression contoursPrepared by contractor: 2 foot increment
Contours
Transect of Raw X-Y-Z Data
Canopy Analysis
Canopy Analysis
MMR LiDAR
Contractor: EarthDataAcquired 15 March 2005About 3-5 meter postingDeliverables include:
2 foot contours (+/- 1ft vertical accuracy)DEM (3m pixel size)X-Y-Z data (25 million records for bare Earth)
Bare Earth and Raw Data
Last Slide
The MMR LiDAR Data:Mediocre 2 foot contoursGreat cartographic enhancementCountless products from DEMsCan be used to detect hidden featuresNot suitable for detecting features less than 3mCan be used for analysis of tree canopiesNot suitable for construction detail
Contact: [email protected]